Thermoregulatory Potential of Sodium Bicarbonate for Lactating Cows under Thermal Stress

Heat stress occurs when the temperature exceeds +25°C (THI ≥ 77). It reduces milk yield and worsens the welfare of dairy cattle. This research featured methods that minimize the effects of heat stress in mild climate. As a buffer additive, sodium bicarbonate can stabilize metabolism and increase the resistance of animals to stress factors. The experiment was conducted on 30 lactating Holstein cows under simulated thermal stress (+30°C, humidity 65–70%). Sodium bicarbonate was administered with morning feed in doses of 150 g (group 1) and 200 g (group 2). The microclimate parameters were monitored by Hobo U12-012 sensors. The analysis indicators included milk yield, milk quality (fat, protein, somatic cell count), and hematological parameters (leukocytes, glucose, hemoglobin). The data was processed using variation statistics. The addition of 200 g of sodium bicarbonate could reduce the drop in daily milk yield to 9.1% (vs. 13.5% in the control group), as well as minimized changes in milk fat and protein by 0.20 and 0.17%, respectively. The level of somatic cells increased by only 15% (vs. 30.56% in the control). The hematological analysis showed steady leukocytes (a decrease of 0.93%) and a moderate increase in glucose (by 2.5%), which was used as a stress biomarker. The data obtained were consistent with similar studies conducted in tropical regions; however, the doses were adapted to short-term thermal stress in mild climate. In this research, 200 g sodium bicarbonate per day reduced the negative effects of heat stress on milk yield and the physiological state of cows. The developed functional and structural scheme of response makes it possible to integrate the temperature and humidity index and hematological data into digital microclimate management systems, thus providing a tailored approach to dairy cattle farming. The results may facilitate the technological optimization of dairy cattle diets in conditions of seasonal climatic fluctuations.